The OSUCCC Analytical Cytometry Shared Resource (ACSR) provides the means of rapidly and accurately analyzing multiple characteristics of biological particles while also being able to rapidly, accurately, and with high purity (>98%) sort out pure populations of cells of interest based on parameters designated by the investigator. This service furthermore provides the OSUCCC members with the ability to obtain viable, sterile, and pure populations of cells so that they may be individually cloned, can be assessed for immunological function, or can be examined for specific biochemical properties with minimal manipulations, compared to magnetic bead technologies. The ACSR has three primary goals: 1) Provide instrumentation and technical operation/support for cell identification/characterization and separation to OSUCCC members and the university community, 2) Provide "applied research" support to address "atypical" or unique/difficult cell identification/separation problems, 3) Introduce the membership to new cell identification/separation technology and methodologies that are being developed at OSU and other institutions/organizations. The ACSR currently has four flow cytometry instruments, one of which was recently purchased and upgraded with a state-of-the-art flow sorter from Becton-Dickenson. Two other flow cytometer analyzers are available for independent (24 hour access) and operated-assisted analysis. In addition, commercial and Jrototype magnetic separation and analysis equipment is available. )ver the last five years, hourly usage of the ACSR has increased 560%, from 937.5 hours in 1998 to over 5,251 hours in 2003. CCSG peer-reviewed funded OSUCCC members account for 88% of the total usage and represent all six OSUCCC scientific programs. This ACSR continues to provide critical support to the scientific programs, now including research data on clinical studies, and contributes to outstanding scientific cancer research as the OSUCCC expands its research portfolio.